1910.] The Mncw.scelidida'. 283 



Skeleton. — The Macroscclididne are terrestrial, saltatorial and more or 

 less fossorial in habit and structure, paralleling the Peramelidfe. These 

 habits are reflected in the following modiflcations in the skeleton of 

 Macroscelides: (1) forearm long and slender, with fused radius and ulna; 

 (2) pes elongate; (3) femur short; (4) fibula reduced and fused with the 

 tibia; (5) ilium erect; (6) pubic symphysis short; (7) lumbar and sacral 

 spines large; (8) back arched; (9) neck short; (10) head held sharply in- 

 clined to the neck. In the pes the astragalus has a deep trochlea with a 

 prominent projecting internal rim. The digits are very elongate but com- 

 pare in essentials with those of Tupaia. In Rht/nc)ioci/on and Petrodromus 

 the hallux is wanting. In Rhyucocyon (cf. Peters 1852, Taf. xxiii) the 

 skeleton is in many features intermediate between those of Tupaia and 

 Macroscelides. 



The vertebral formula, as determined from de Blainville's figure of 

 Macroscelides rozetii is C 7, D. 13, L 7, S. 3, Cd. 26. Mivart states (1867, 

 p. 298) that both Peters and de Blainville assigned 7 lumbar vertebrae to 

 this genus, but also that in a certain specimen of M. intufi there are but 19 

 dorsolumbars. Accordingly Macroscelides may be regarded as having 19 

 to 20 dorsolumbars, whereas Tupaia has 18 to 20 (Mivart, op. cit., p. 294). 

 In Rhynchocyon cmiei the formula is: C.7, D.13, L.8, S.3, Cd. 28 (cf. Peters 

 I.e., Taf. xxiii) i. r, DL. 21. 



The carpus of Rhynchocyon is noticed below (p. 445). 



Phyletic interpretation of the more important characters of the Macroscelididce. 



Primitive Marsupio-Placental Characters. Testes remaining abdominal; 

 brain and Jacobson's organ very primitive in certain features. 



Special resemblances to the Marsupials: brain with a "typically meta- 

 theroid commissure" etc.; Jacobson's organ of Marsupial type; malar 

 extending back to glenoid fossa; large palatal vacuities; alisphenoid 

 scarcely overlapping the orbitosphenoid (Parker); optic foramen more or 

 less confluent with for. lac. anterius; a concave tympanic process of the 

 alisphenoid {Rhynchocyon); vomer with large postero-lateral wings. 



Primitive Placental characters: a corpus callosum; placenta discoidal 

 deciduate (Broom, 1902, p. 227); dentition derived from |^;|j^; by the loss 

 of one or more molars ; manus pentadactyl [Petrodromus only) ; carpus with 

 free centrale. 



Primitive Inscctivore characters. A long cartilaginous snout; pre- 

 maxillaries elongate, canines more or less premolariform; p| molariform; 

 a large interparietal; a median (chordal) perforation in the basisphenoid 

 {Rhynchocyon); pterygoids terminating in small cartilages; stapes perforated 



